Data from wind power plants are received by a central computer system from the plurality of wind turbines forming the wind power plant as well as from other parts, such as wind anemometers, power output meters etc. with the purpose of surveying the performance and operation of the power plant and for producing reports of the performance. The latter is important as the contracts between manufactures and owners of the power plant usually are based on a set of performance parameters that are evaluated from such reports. The wind turbines report their operational parameters, e.g. power production, pitch angle of the blades, local measured wind speed and direction, temperatures of the generator, power transformer etc., angle of yaw, as well as the operational status, i.e. the categorisation of the time period of the data, such as “normal operation”, “yawing”, “turning of nacelle to recoil cables”, “no contact with power grid”, failures of different types etc. In particular, the operational status is important for non-productive periods, so-called downtime because the amount of downtime due to failure of the wind turbines is a significant parameter in computing the performance of the wind power plant. The reporting from the wind turbines is made regularly, typical every 10 minutes, and these data are called raw data.
The quality and completeness of the raw data is normally not satisfactory for direct generation of reports and manipulation of the raw data is performed by overwriting the raw data with corrected data to estimate missing data, correct erroneous data, e.g. values being out of a reasonable range or categorisation data, in particular downtime due to specific causes externally to the power plant. This correction of the raw data is performed as a series of automated routines each correcting for different faults according to a specific method, supplied with a number of manually generated corrections. Thus, the final data from which the reports are generated may typically comprise a considerable amount of data that have been added, altered or corrected one or several times.
Although a copy of the raw data usually is saved as a separate database file, the history of corrections is normally lost and the relation between the measured data and the corrected data may only be resolved by comparing the final data with the raw data.
It has been found by the present inventors that it is advantageous to be able to provide a more detailed substantiation of the corrections made to the raw data in order to generate the performance reports so that the credibility of the report can be estimated. Furthermore, it has also been found to be advantageous to facilitate the generation of different reports in order to evaluate different aspects of the performance and operation of the wind power plant, e.g. for optimisation of different aspects of the operational parameters, for identifying the importance of various reasons for downtime and for evaluation of the plant performance according to a set of contractual rules.
A separate log of the corrections may be kept and a backtracking of each of the final data by means of the log may be applied to generate each of the different reports and the substantiation of the corrections. However, this procedure is tedious and requires many calculations and database lookups, particularly for the large amounts of data originating from large wind power plants over long time periods of several months or even years. The request for generation of different reports based on different corrections or priority of the corrections may necessitate that a separate series of corrections starting from the raw data is performed for each of the reports.